Gustavo,
I am sorry I can not provide the entire code for you because it's in our another product MapSuiteRouting. The point is that you can use ValueStyle to draw different icon and use TextStyle to draw the number. Here is the sample code:
// This layer contains the column "Key" which value is {1,2,3...}.
ShapeFileFeatureLayer pointsLayer = new ShapeFileFeatureLayer(shapePathFilename);
pointsLayer.ZoomLevelSet.ZoomLevel01.CustomStyles.Add(new TextStyle("Key", new GeoFont("Arial", 10), new GeoSolidBrush(GeoColor.SimpleColors.Black)));
pointsLayer.ZoomLevelSet.ZoomLevel01.ApplyUntilZoomLevel = ApplyUntilZoomLevel.Level20;
// Set icon images based on values
ValueStyle valueStyle = new ValueStyle();
valueStyle.ColumnName = "Key";
valueStyle.ValueItems.Add(new ValueItem("1", new PointStyle(new GeoImage(geoImage1))));
valueStyle.ValueItems.Add(new ValueItem("2", new PointStyle(new GeoImage(geoImage2))));
valueStyle.ValueItems.Add(new ValueItem("3", new PointStyle(new GeoImage(geoImage3))));
pointsLayer.ZoomLevelSet.ZoomLevel01.CustomStyles.Add(valueStyle);
Please let me know if that is not clear.
Thanks
James